Means for starting and regulating induction-motors.



No. 739,096. PATENTED SEPT. 15, 1903.

' R, 1). DE' LIGNIERES; I MEANS FOR STARTING AND RBGULATING INDUCTIONMOTORS.

APPIIUATIOK IILIID NOV. 9, 1901.

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R. D. DE Lwmfinzsf MEANS FOR, STARTING ANDREGULATING INDUCTION MOTORS.

APPLICATION FILED NOV. 9, 1901. v 7

N0 MODEL. 6 SHEETS-SHEET 2.

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No. 739,096. PATBNTED SEPT. 15, 1903.

R. D. DE LIGNIERBS. MEANS FOR STARTING AND REGULATING INDUCTION MOTORS.

APPLICATION FILED NOV. 9, 1901. 1

N0 MODEL. 5 SHEETS-SHEET 4.

No. 739,096. PATENTED SEPT. 15, 1903.

' Rt 1). DE LIGNIERES.

MEANS FOR STARTING AND REGULATING INDUCTION MOTORS.

APPLICATION rum) NOV. 9, 1901. v

5 SHEETS-SHEET 5.

%M%Q 673.51 d zy z ms Flo. 739,096.

UNITED STATES; PATENT OFFICE."

Patented September 15, 1903;.

RENE DASSY on LIGNIERES, or PARIS, FRANCE.

MEANS FOR STARTING AND REGULATING INDUCTION-MOTORS.

SPECIFICATION forming part of Letters Patent No. 739,096, datedSeptember 15, 1903. v Application filed November 9, 1901- Serial No.81,704. (No model.)

To all whom, it may concern:

Be it known that I, RENE DASSY DE LIGNI- ERES, engineer, a citizen ofthe French Republic, residing at Paris, Seine, France, (whosepost-office address is 169 Avenue de \Vagram, in the said city,) haveinvented certain new and useful Improvements in Means for Starting andRegulating Induction Motors, of which the following is a specification.

This invention has for its object to provide an improved apparatus forstarting and regulating the speed of induction-motors which are fed bysimple or polyphasc alternatingcurrent motors. These motors may beconstructed as follows: One part of the motor (the rotor) is keyed fastto the motor-shaft, while the other part (the stator) is movable aroundthis shaft, and either one part or the other may be employed as thearmature or the inducing-field. The armature and the inducing-field arerespectively the same as those used on the ordinary alternate-currentsimple or polyphase motors and they may have any suitable position withrelation to each other-that is, they may be arranged concentrically orside by side. According to this invention the current is caused to flowby any suitable means into the inducing-field, so as to start the statorwithout load. When the angular speed of thestator has reached about thenormal, which is nearly that corresponding to the synchronism, therotation of said stator is progressively decreased and the rotor startsunder load in a direction opposite to that of the stator. From thismoment the rotor tends to maintain with respect to the stator a relativeangular speed which is nearly constant and equal to that of synchronism,taking into account the variations resulting from the slips of theseveral torques. The proper angular speed of the rotor (which is equalto its angular speed with respect to that of the stator, to which mustbe added the angular speed of the stator) is allowed to vary accordingto the angular speed given to the stator, and according to the presentinvention it may be controlled by means of a suitable adjustable brakingdevice acting on the stator.

I11 order that my invention may be fully same with reference to theannexed drawings, in which.

Figure l is an end view, partly in section, of a motor and brakeembodying my invention. Fig. 2 is a side elevation of the same, partlyin section, the motor being shown in connection with an electromagneticbrake. Figs. 3 and 4 are diagrammatic views illustrating the theory oftheoperation. Fig. 5 is a detail view in elevation, showing a modifiedarrangement for connecting the electromagnetic brake with the motor; andFigs. 6 and 7 are detail views showing two methods of lubricating therotating parts.

Referring to Fig. 1, a represents the stator (I shall presume it to bethe inducing-field) of a motor, whichis loose on the shaft 0 and onwhich shaft is keyed the rotor I), (say the armature in the presentcase.) The current is sent through the rings (1 6 into theinducingfield, which is started by any suitable device. The stator maybe started without load through the agency of anauxiliary motor, whichmay be either electrical or mechanical, preferably the former, and whereelectrical means is employed for starting the stator without load theresult accomplished depends on the obtainment of a dissymmetryin theinducing-winding. Thiswindingmay,forinstance, be divided into two parts,one being at an angle of behind the other, (2p being the A number of themotor-poles,) and each of these parts is fed with the total tension oronly a part thereof, which may be effected by interposing a resistancein one of the parts and in the other part a self-induction. \Vhen thestator has reached to its normal angular speed, which is nearly that ofsynchronism, it may be progressively stopped by means of a brakef,operated in the direction of the arrow.

At the same time that the speed of the stator 1 progressively decreasesthe rotor 1) begins to' nism when the brake has entirely stopped theThis speed will be brought to zero if v stator.

the brake is entirely released. In the construction shown in thedrawings the current been effected.

is supposed to be sent to the inducing-field as through two rings d and8 only, corresponding to the principal winding of the inducing field,which in many cases is the only active winding when a starting with noload has For the purpose of effecting a starting without load most ofthe devices iitherto in use require the employment of at least one otherring corresponding to one end of the winding especially intended forstarting, the other end being connected with a fourth ring or with oneof the two rings d e or even with some point of the principal Winding ofthe inducing-field between the rings d 6. It is essential that thebraking action on the stator be a progressive one; otherwise risk wouldbe run of falling upon the descending curve of the torque of the motor,and the stator would be completely stopped without effecting thestarting of the rotor, and at the same time the intensity of the currentin the inducing-field would be excessive.

If a curve of the torque of an inductionmotor in operation be drawn todetermine the slippage of the armature with respect to the movable fiux(in the case of simple alternating currents, as shown in Fig. 9)'or ofthe total movable flux, (in the case of polyphase currents, as shown inFig. 10, )this curve,when the armature does not slip, has a negative andvery small value in the case of simple alternating currents or a nullvalue in the case of polyphase currents. Fig. 9 of the drawingsillustrates the torque curve of an induction-motor in the case of simplealternating currents with respect to slippage and to the movable flux,and Fig. 10 is an illustration of the torque in the case of polyphasecurrents. The value of the torque increases in the latter instance veryrapidly, passing through the zero-point for small slippages in the caseof simple alternating currents. \Vhere the slippage increases, thetorque is positive and increases(ascending curve) up to its highestvalue, which is obtained from a relatively small value of the slippage,(practically from 0.0 to 0.0 If the slippage increases, the value of thetorque diminishes proportionately (descending curve) and passes throughthe zero-point, the slippage being equal to the unity of power in thecase of alternating currents and for an endless slippage in the case ofpolyphase currents. The stator of this motor is first given an angularspeed which nearly corresponds to the synehronism,so that the usefulmovable flux (or the total movable flux) is practically fixed withrespect to the armature. The starting of the rotor is secured byprogressively decreasing the speed of: the stator when the slippage ofthe useful movable fi'ux increases with respect to the armature. It isobvious that the braking action of the stator must be a progressive onein order that the stator has the necessary time to acquire requisiteacceleration, so that the slippage of the armature with respect to thehereinafter described.

movable flux has never a higher value than the one corresponding to theresisting torque represented by the descending curve, for the reasonthat if the slippage be of a higher value and braking action be toosudden the speed of the rotor would decrease too rapidly and slippagewould then increase, causing the torque again to decrease until therotor would stop.

Any form of electromagnetic brake may be used, comprising a stationarypart (stator of the brake) and a movable part (rotor) movable with thestator of the motor, the connection between the rotor of the brake andthe stator of the motor being either direct or through suitableinterposed gearing. One of the two partsfor example, the armatureof theelectromagnetic brake is identical with the armature of aninduction-motor provided with a rotating magnetic field, (of thesquirrelcage pattern or polyphase armature with or without resistance.)The other part-that is,

the inducing-field-produces a magnetic flux or a series of magneticfluxes of constant direction, the same being formed by windings, whichare traversed by a continuous current. This inducing-field may bemassive ornot, as desired, and is provided with projecting poles orpoles of an annular form, and as the fluxes it produces (as well asthose resulting from its action) are stationary with regard to the saidinducing-field it can be subjected to great inductions. If theinducing-field is of an annular form, its windings can have any of theforms adopted for the principal inducingwindings of simplealternating-current asynchronous induction-motors. The inducingfield orthe armature of the electromagnetic 1 brake m ay be the rotor or thestator, and their relative arrangement may be effected in any convenientmanner-that is, they may be arranged either concentrically or side byside. In Fig. 2 the inducingfield h of the brake constitutes the rotor,and the stator a (inducing-field) of the motor is directly connected 5therewith.

5 stationary.

The armature g of the brake is As stated above, the inducingfield a isstarted without load by any convenient meansfor instance, by one ofthe-means \Vhen the inducingfield a rotates, the inducing-field hisrotated at the same speed or at a speed in a certain ratio therewith. Itmay therefore be supposed that the armature g is movable with respect tothe stationary fields, thus producing induced currents in said-armature.A retarding torque is also created, which is a function of the amount ofexcitation in h of the angular speed of the armature g with regard tothat of the field h and of the resistance of the polyphase circuits ofthe armature g. It is easily understood that for a given resistingtorque on the shaft 0 the inducing-field a can be braked, more or less,either by operating the rheostat 1', which controls the intensity of theexcitation in the armature h, or by acting on the resistances verysimple manner, as they only require the operation of rheostats. In thismanner I control the proper angular speed of the armature of the motorfor a given torque. It is obvious that the'motor may have any suitabledisposition with respect to the electromagnetic brakethat is, these twoparts may be concentric or side by side.

The theory of operation of the electromagnetic brake above described issimilar to that of a motor with a revolving magnetic field, theinducing-flux of which is constant for a determined value of theexciting-current and opposed to that of a motor with a rotating magneticfield fed with single or polyphase alternate currents of a constantvoltage, in.

which latter class of motors the resulting flux is nearly constant.Moreover, in this electromagnetic brake the inducing-flux instead ofbeing movable, is stationary with regard to the inducing-core. For thesake of simplicity assume that the ind ucing-winding, excited by acontinuous current, creates an inducingfiux Q Fig. 3, which is constantfor a determined value I of the continuous inducingcurrent. For the sakeof more simplicity in the following theory suppose the armature g bemovable with respect to the stationary inducing-field h in opposition tothe arrange ment shown in Fig. 2. From the rotation of the armature withrespect to the inducingfield a flux Q results which is constant for agiven speed and will be stationary if 4 is stationary. From the rotationof the armature with respect to the resisting-flux currents result inthe armature which produce an induced flux Q, at an angle of ninetydegrees behind Q, account being taken of the direction of rotation of9?, with respect to the armature. Now the inducingfield being stationaryand the armature rotating iii the direction of the arrow 1, the fluxesQ, and 4 which really are stationary, will rotate with respect to thearmature in the direction of the arrow 2. The flux 4 will take thedirection O A (shown by Fig. 3) at an angle of ninety degrees behind 91The inducingflux C is such that 'the resultant of its composition withQ, is Q. It therefore is represented by the segment 0 I, equal andparallel to A R. It is then seen that for; a constant value of if, thepoint R will move on a circumference having'a diameter 0 I: and everyposition of the said point B gives:

RT: ii,

Let 0- be the resistance of the induced polyphase winding of an,accurately-determined fraction of the induced polyphase winding of thebraking apparatus. If 7/ designates the slip of the armature withrespect to the indncing-field'and s s quantities of a constant value, wecan write: I

whence r 1 t a. (1)

The torque IV will be \V=s. Q Q ,-=s. @Ktga; (2)

From this equation the value of the flux can be obtained, and thereforethe minimum value of the exciting-current necessary (but not sufficient)for producing a braking action: I05

In this latter equation 7 designates the resisting torque applied to themotor in the case of a direct connection of the motor and theelectromagnetic brake. i

In polyphase-current motors the inducingcurrents, if harmonics are notregarded, pro duce a movable flux having a direction of rotation that iswell understood. In simple alternating-current motors the inducing-cur:rent produces an alternating fiiix which can be decomposed into twofluxes turning in opposite directions, a useful flux which rotates inthe direction which is to be imparted to the armature, and aparasiticalflux. In polyphase motors the parasitical fl uxes annul each other andthe movable flux has only one direction of motion.

I am aware that in motors having revolving magnetic fields fed bycurrents under a constant tension it is necessaryfor the purpose ofobtaining a given starting torque that the resistance of the circuits inthe armature have a determinated value. In the present case a similarcondition exists-the ohmic resistance or the apparent resistance of thecircuits in the armature must have a sufficient value for securing thebraking for a given resisting torque applied on the armature of themotor. All the methods hitherto in use, according to which the startingand the regulation of the speed of motors with revolving magnetic fieldsresult from an action on the induced windings, can therefore easily beapplied to the present electromagnetic braking device, although in thiscase the inducing-flux instead of the resulting flux be practicallyconstant.

The operations may naturally be simplified by giving the resistances ofthe induced windings a sufficient value for always securing the startingwithout the employment of slipping contacts; but in this case the slipof the electromagnetic brake during the normal working is greater. Inorder to reduce as far as possible the slip of the movable part of thebrake in the normal working, the continuous exciting-current mustbeincreased to its maximum value. At least for having a perfect brakingaction during the normal working that is to say, for reducing to zerothe slip of the movable part of the electromagnetic brake-a mechanicalbrake operated by a mechanical or electric device can be applied on thispart. As far as possible this mechanical brake must be arranged so as toproduce only a tangential action on the part to which it is applied, asshown in Fig. 4, wherein the straps are stretched in the direction ofthe arrows.

An electromagnetic brake of the kind described can be generally appliedin the same manner as a friction-clutch with variable slip, thevariations of which may be well determined. One of its parts-71, forexample, Fig. 5is connected with the driving part b, the other part, g,being connected with the shaft to be set into motion. This brake couldalso be applied to a single alternating current motor, of which Z) isthe rotor and a the stator, Fig. 5, the stator a being alwaysstationary. The rotor 11 is started without load, and when its speed ofrotation has reached nearly that of synchronism the brake isprogressively operated by controlling the continuous current, whichexcites the clutch and the resistance of its induced part.

Generally speaking, for starting the motor without load, whether it isfed with single or polyphase alternating currents, two distinctmethodscan be employed according towhether or not the induced winding beconnected with variable resistances or to whether or not itis of anyconvenient polyphase or short circuited kind. In case the induced winding is connected with resistances the starting can be elfected by feedingthe inducing-circuits with the whole of the normal potential difference,and an excessive consumption of current will be avoided by acting on theresistances interposed in the circuits of the armature.

Fig. 1 illustrates one form of embodiment ofthe invention for effectingstarting of the stator without load. The inducing-winding shown in fulllines in Fig. 7.

of the motor is divided into two parts a and a disposed atan angle ofabout to each other, 2p indicating the number of poles. Simultaneouslywith the starting of the stator connections are established through theagency of atwo-direction commutator in order that a resistance 0 may beincluded in the circuit a and a self-induction Z in the circuit a thecircuits at and a being fed with the total feeding tension,thehand-levers of the commutator c, in this instance, being in the positionThe induced winding 1) of the motor is polyphase and is connected with apolyphaserheostat (Z, it being necessary before causing the current topass for starting the motor without load to set the hand-lever of therheostat (Z in the position corresponding to the highest values of theresistances and to cause the highest value of these resistances todecrease in proportion as the speed of the motor increases until thecircuits of the armature are finally shortcircuited. WVhen the startingwithout load is obtained, the hand-levers of the commutator are set inthe position shown by dotted lines in Fig. 7 and the two parts a and aof the inducing-winding are then connected in parallel and theresistance r and also the selfinduction Z are short-circuited. 111 thecase of a polyphase short-circuited induced winding the starting iseffected by feeding the inducing-circuits only with asufficiently-reduced potential difference, and in this case the yieldingof the armature of the motor will be increased.

Fig. 8 illustrates another form of embodiment of the invention foreffecting starting without load and corresponds with Fig. 7, which ismodified in the case of the armature I) having polyphase windings whichare shortcircuited. The starting without load will always be effected byinterposing a resistance r in one of the parts a of the inducing-windingand a self-induction Z in the other part a but it is necessary at thebeginning of the starting to feed the circuits (1. and a only with asufficiently-reduced part of the potential difference by means ofatransmitter 25 of variable tension, which in the case of the abovefigure is a transmitter having a single winding. Potential difference isprogressively increased by setting the hand-lever of the transmitter tin proportion as the angular speed of the stator increases. l/Vhen thestarting is effected, both of the parts a and a of the illducing-windingare connected again in parallel by means of the switch 0.

Having now particularly described and ascertained the nature of myinvention and in what manner the same may be performed, I declare thatwhat I claim is- In an apparatus for starting and regulating the speedof alternating-current motors, a rotary shaft, having the stator of themotor loosely mounted thereon and the rotor of the motor keyed thereto,means for starting the IIO I I i l intensity of the current in saidinducin g-field by varying the resistances interposed in the circuits ofsaid armature, or by effecting these two operations simultaneously.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

RENE DASSY DE LIGNIERES.

Witnesses:

EDWARD P. MAoLEAN, EMILE KLOTZ.

